The present invention relates to a switch for stopping the shifting movement of a crankshaft immediately after the proper balance centering thereof has been determined.
A device of the general nature mentioned above is discussed in German Patent No. 28 23 219 (U.S. Pat. No. 4,300,197 the disclosure of which is incorporated herein by reference), which concerns a procedure and a device for centering of rotational bodies with non-uniform mass distribution along the shaft axis. The surface of those rotationally symmetrical parts which contain the shaft axis are radially sensed by means of mechanical sensors. The purpose of this sensing is to guarantee a displacement of a crankshaft until a minimal rotation radius has been obtained for one point on the surface of two selected crankshaft sections rotating around the axis of the balancing machine without eccentricities due to the system. Should such a sensing not take place, there would be a danger that, given the extreme unbalance of a raw crankshaft, it would be possible to balance the crankshaft with corresponding guidance, but that rejections would occur in later mechanical processing of the main bearing necks or crank pins due to an occurring great geometrical eccentricity in the geometrical axis of the crankshaft. Since the minimum permissible rotation radius r.sub.e of a point on the surface of the crankshaft section to be machined may not be obtained, e.g. due to a slanting of the geometrical crankshaft axis, rejections are likely in later mechanical processing.
The manufacturing of a crankshaft involves molding or forging the preliminary component. A component of this type is called raw crankshaft. As a result of the molding or forging, this raw crankshaft has a non-uniform mass distribution along the axis of the shaft. This raw crankshaft can now be placed on a milling machine, the required positions can be turned and ground on the milling machine, and the completed crankshaft can then be brought to a balancing machine where the unbalance of this crankshaft can be determined. It will then be found that a great proportion of the finished crankshafts have such an unbalance that it is no longer possible to compensate for this, since that space in the motor where the shaft can rotate is limited. From this, it is apparent that such a procedure is definitely not economical.
U.S. Pat. No. 2,746,299 (incorporated herein by reference) and above noted U.S. Pat. No. 4,300,197 describe how this obvious disadvantage can be eliminated. This is achieved by placing the raw crankshaft in a dynamic centering machine before it is mechanically processed. This centering machine accommodates the raw crankshaft in two bearings, each of which can be moved in one plane by means of motors. When the crankshaft is positioned and the centering machine begins to turn, the unbalance vibrations are recorded in the movable bearings via vibration recorders connected to the centering machine. In response to the information from the vibration converters, the motors that reset the positions are activated, and the specific end of the raw crankshaft is displaced until the vibration converter no longer measures an unbalance. Accordingly, the raw crankshaft has been brought into such a position after being moved at both ends by means of the movable bearings such that the resulting rotation axis stands at an oblique angle to the original rotational axis of the raw crankshaft. This obliquely angled axis is used as a geometrical axis for later processing and is then counterbored by means of drills so that the indicated geometrical axis serves as zero axis for later measurement of the balance of another machine (e.g. balancing machine). This axis is also the rotational axis of the finished shaft.
Other devices and procedures for balancing elongated bodies such as crankshafts, which have been mentioned in the above cited disclosure documents, do not include any device for measurement and control of the minimum rotational radius.